Location Estimation Method and Apparatus Using Access Point in Wireless Communication System

1. A method of operation for a location estimation apparatus communicating with an access point (AP) in a wireless communication system, the method comprising: receiving a first received signal strength indicator (RSSI) signal measured at a first AP via a second AP, and generating a first RSSI vector corresponding to the first RSSI signal; calculating a path loss exponent using a distance between the first AP and the second AP and the first RSSI vector, and generating a second RSSI vector for each of multiple sub-regions constituting an entire region based on the path loss exponent; and generating a radio map for the entire region based on the first RSSI vector and the second RSSI vector.

2. The method of claim 1 , wherein the location estimation apparatus is one of an AP controller and an AP server for controlling the APs.

3. The method of claim 1 , further comprising: generating a third RSSI vector corresponding to a second RSSI signal measured by a wireless device; and estimating a location of the wireless device in the radio map based on a cosine similarity between the second RSSI vector and the third RSSI vector.

4. The method of claim 3 , wherein estimating the location of the wireless device comprises: calculating the cosine similarity between the second RSSI vector and the third RSSI vector, and selecting a sub-region having a largest cosine similarity from among the sub-regions; and estimating that the wireless device is located where the selected sub-region is located in the radio map.

5. The method of claim 4 , wherein the cosine similarity is calculated for first sub-regions located within a preset distance from the second AP among the sub-regions.

6. The method of claim 1 , wherein generating a second RSSI vector for each sub-region comprises generating the second RSSI vector by adding an offset calculated using Equation 5 to the first RSSI vector, x = n ⁢ ⁢ log ⁢ d ⁡ ( C 0 , AP i ) d ( C 1 , AP i ) [ Equation ⁢ ⁢ 5 ] where x is the offset, n is the path loss exponent, C 0 is an initial sub-region, C 1 is a target sub-region, AP i is the second AP, d(C 0 ,AP i ) is a distance between the initial sub-region and the second AP, and d(C 1 ,AP i ) is a distance between the target sub-region and the second AP.

7. The method of claim 1 , further comprising: normalizing the first RSSI vector and storing the normalized first RSSI vector in the radio map; and normalizing the second RSSI vector and storing the normalized second RSSI vector in the radio map.

8. The method of claim 1 , wherein the first AP and the second AP are adjacent to each other, and wherein the first RSSI signal is transmitted from the first AP to the second AP.

9. An apparatus for location estimation capable of communicating with an access point (AP) in a wireless communication system, comprising: a transceiver unit configured to receive a first received signal strength indicator (RSSI) signal measured at a first AP via a second AP; and a radio map generator configured to generate a first RSSI vector corresponding to the first RSSI signal, calculate a path loss exponent using a distance between the first AP and the second AP and the first RSSI vector, generate a second RSSI vector for each of multiple sub-regions constituting an entire region based on the path loss exponent, and generate a radio map for an entire region based on the first RSSI vector and the second RSSI vector.

10. The apparatus of claim 9 , wherein the apparatus is one of an AP controller and an AP server for controlling the APs.

11. The apparatus of claim 9 , further comprising a location estimator configured to generate a third RSSI vector corresponding to a second RSSI signal measured by a wireless device, and estimate a location of the wireless device in the radio map based on a cosine similarity between the second RSSI vector and the third RSSI vector.

12. The apparatus of claim 11 , wherein the location estimator is configured to calculate the cosine similarity between the second RSSI vector and the third RSSI vector, select a sub-region having a largest cosine similarity from among the sub-regions, and estimate that the wireless device is located where the selected sub-region is located in the radio map.

13. The apparatus of claim 12 , wherein the location estimator is configured to compute the cosine similarity for first sub-regions located within a preset distance from the second AP among the sub-regions.

14. The apparatus of claim 9 , wherein the radio map generator is configured to generate the second RSSI vector by adding an offset calculated using Equation 6 to the first RSSI vector, x = n ⁢ ⁢ log ⁢ d ⁡ ( C 0 , AP i ) d ( C 1 , AP i ) [ Equation ⁢ ⁢ 6 ] where x is the offset, n is the path loss exponent, C 0 is a initial sub-region, C 1 is a target sub-region, AP i is the second AP, d(C 0 ,AP i ) is a distance between the initial sub-region and the second AP, and d(C 1 ,AP i ) is a distance between the target sub-region and the second AP.

15. The apparatus of claim 9 , wherein the radio map generator is configured to normalize the first RSSI vector and store the normalized first RSSI vector in the radio map, and normalize the second RSSI vector and store the normalized second RSSI vector in the radio map.